In the case that theendofday is considering, there is not an alternator available to provide that baseline 160amp flow (unless he runs power in from his car and leaves the engine running), so he would be using the batteries in parallel to produce all of the current for the system. If we take a trio of batteries in parallel, that would be either an 8.25 amp load for 20 hours (which wouldn't offer much) or up to 75 amps for only two hours. For brief demos in a store, that would probably be pretty effective - running at a very low level for most of the day with brief spikes up to a very high level would probably not drain the batteries until near the end of the day. For use in a 5.1 channel home theater, it may be fine for prolonged two-channel listening or watching TV at moderate volumes, but you may also find yourself stopping at the end of the first disc of the extended edition of Return of the King to recharge batteries before continuing with the second disc.